Liquid-vapor equilibrium and critical point of parabolic-well fluids of variable width derived from Gibbs Ensemble Monte Carlo simulation

Abstract

The vapor-liquid coexistence curve at equilibrium of parabolic-well (PW) fluids is computed by means of Monte Carlo simulations, for a selection of well-widths. The outcome is compared with results for corresponding curves of triangle-well (TW) and square-well (SW) fluids with the same range. It is found that, for a given width, the shape of the vapor-liquid coexistence curve in the case of the parabolic-well fluid is rather similar to the one of the triangular-well fluid and a little bit different to the one of the square-well fluid. It is also found that such vapor-liquid coexistence curve shifts towards higher temperatures as the width of the parabolic-well potential increases, always falling, for the same range in all cases, between the vapor-liquid coexistence curves corresponding to the other two potentials. In addition, it was observed that the reduced critical temperature matches the theoretical prediction of the Vliegenthart and Lekkerkerker (V-L) criterion only for the smaller well-width, the accuracy of such criterion decreasing substantially as the range increases.